番木瓜性别决定及其鉴定研究新进展

番木瓜有3种基本性别类型,性别遗传较为复杂.就其植株的多型性表现、性别决定及其鉴定研究、连锁遗传图的构建、分子标记辅助选择技术和花器的发育等方面的研究进展进行了综述,并对番木瓜性别鉴定的应用前景做了展望.     

番木瓜性别分化研究进展(综述)

番木瓜性别分化是植物发育生物学的研究热点之一。本文从形态学及细胞学、遗传及基因组、性别分化调控等方面对番木瓜性别分化研究概况进行综述及展望。     

Cyanogenesis in glucosinolate-producing plants: Carica papaya and Carica quercifolia

(R)-2-(beta-D-Glucopyranosyloxy)-2-phenylacetonitrile (prunasin) was isolated from Carica papaya L. and C. quercifolia (A. St.-Hil.) Hieron. (syn. C. hastata Brign.). Earlier reported presence of cyclopentanoid cyanohydrin glycosides in C. papaya could not be confirmed, and no cyclopentanoid amino acids could be detected in extracts of C. papaya and C. quercifolia. Conversion of [2,3,4,5,6-3H]phenylalanine into tritiated prunasin was demonstrated in both species. On the other hand, when the plants were administered [2-14C]-2-(2'cyclopentenyl)glycine, extracted, and the extracts hydrolyzed with beta-glucosidase (Helix pomatia), formation of labelled cyanide was not observed. The absence of cyclopentanoids, which are typical for the Passifloraceae, and the inability of Carica species to utilize 2-(2'-cyclopentenyl)glycine as a precursor of cyanogenic glycosides are in agreement with the relative phylogenetic position of the Caricaceae and the Passifloraceae. Carica species are thus rare examples of taxa in which glucosinolates and cyanogenic glycosides co-occur, both types of natural products being derived from the same amino acid, phenylalanine.     

银杏幼苗雌雄株对盐胁迫响应的差别

采用对盆栽银杏(Ginkgo biloba)雌雄幼苗浇灌NaCl(40?mmol L-1)溶液模拟土壤受盐胁迫的方法,研究银杏雌雄幼苗气体交换特征、内在水分利用效率(WUE)、游离脯氨酸含量(Pro)、超氧化物歧化酶(SOD)及过氧化物酶(POD)活性在盐胁迫下的差异.结果表明:(1)盐胁迫后雌株的净光合速率、气孔导度以及蒸腾速率与对照相比分别降低45.87%、25.00%、16.47%,而雄株的气孔导度、胞间CO2浓度和蒸腾速率分别升高了10.00%、8.10%、22.95%;(2)盐胁迫显著降低了银杏幼苗的WUE(P=0.020),与对照下相比,雌、雄WUE分别下降30.47%、46.38%;(3)盐胁迫显著提高了雄株的游离Pro含量,但对雌株影响不显著;(4)盐胁迫使银杏雌、雄幼苗SOD活性分别降低了22.96%、23.18%,但下降幅度均不显著.然而盐胁迫会显著降低雌株的POD活性,但对雄株无显著影响.上述结果同时表明,40?mmol L-1的NaCl溶液不仅会降低银杏雌雄幼苗的光合速率,影响气体交换,还会降低WUE、SOD及POD等酶活性,提高游离Pro含量,但雌株受到的负面效应小于雄株.与雄株相比,雌株在盐胁迫下能通过维持较高的光合速率贮藏能量,较低的蒸腾速率和较高的内在水分利用效率以减少水分散失,以及较高的抗氧化物酶活性来缓解盐胁迫带来的氧化胁迫,使其受到的负面影响减小.     

Localization of benzyl glucosinolate and thioglucosidase in Carica papaya fruit

Macerated papaya seeds and pulp contained benzyl isothiocyanate, produced by the enzymatic hydrolysis of benzyl glucosinolate by thioglucosidase. The substrate and enzyme were localized in different areas. In mature papaya seeds, thioglucosidase was found in sarcotestae but not in endosperms, while the reverse was true for benzyl glucosinolate, which constituted more than 6% (w/w) of the endosperms. Both the enzyme and substrate were present in embryos and the amount of the latter was 3·9% (w/w). In immature papaya pulp, benzyl glucosinolate was localized principally, if not exclusively, in the latex, ranging from 7·3 to 11·6% of the dry wt of latex fluid. No thioglucosidase activity was found in papaya latex. The possible significance of the localization of this enzyme-substrate system and aspects concerning functions of papaya latex are discussed.     

Field biology and control of Phytophthora parasitica on papaya (Carica papaya) in Hawaii

Epidemic attacks of Phytophthora parasitica on papaya fruits developed during wet, windy weather, but declined rapidly when the weather became dry. During rain, abundant sporangia were liberated from the mycelial mats on infected fruits, but none was trapped in dry air. Collar rots and tree collapse caused by root rot occur irrespective of spray treatments and previous aerial infections on the same tree: they are no more prevalent in blocks with abundant aerial infections than in blocks with none. Basal rots occurred earlier and more frequently on plantings near abandoned diseased fields: they were scattered randomly and appeared before aerial infections. It is suggested that new outbreaks might be initiated from seeds of infected fruit, in which chlamydospores have been found, or from infected nursery seedlings. Drosophila spp. were found to be occasional vectors of sporangia. Control of aerial infections was obtained with maneb, basic copper sulphate, captan or difolatan. Spraying only the upper half of the acropetally developing fruit cluster gave much better control than spraying only the lower fruits.     

Responses of Papaya Seedlings (Carica papaya L.) to Water Stress and Re-Hydration: Growth, Photosynthesis and Mineral Nutrient Imbalance

The effects of water stress and subsequent re-hydration on growth, leaf abscission, photosynthetic activity, leaf water potential and ion content were investigated in papaya seedlings (Carica papaya L.) cv. “Baixinho de Santa Amalia”. Water stress was imposed by suspending irrigation during 34 days. Thereafter, plants were regularly re-watered. Drought arrested plant growth, induced leaf abscission and drastically decreased photosynthetic rate. However, leaf water potential was hardly reduced. Water deficit also induced sodium, potassium and chloride accumulation in leaves and roots, and did not modify nitrogen levels in both organs. Re-hydration stimulated growth, promoted emergence of new leaves, reactivated photosynthetic machinery function and reduced ion content to control levels. The results indicated that the ability of papaya plants to improve drought tolerance is not mediated through the reduction of leaf abscission, the detention of growth or the decrease of net CO₂ assimilation. In contrast, the data suggested that under water stress conditions these plants appear to posses a certain capacity to increase ion content, which might contribute to osmotic adjustment.     

Carpeloidy in flower evolution and diversification: a comparative study in Carica papaya and Arabidopsis thaliana

Background and Aims

Bisexual flowers of Carica papaya range from highly regular flowers to morphs with various fusions of stamens to the ovary. Arabidopsis thaliana sup1 mutants have carpels replaced by chimeric carpel–stamen structures. Comparative analysis of stamen to carpel conversions in the two different plant systems was used to understand the stage and origin of carpeloidy when derived from stamen tissues, and consequently to understand how carpeloidy contributes to innovations in flower evolution.

Methods

Floral development of bisexual flowers of Carica was studied by scanning electron microscopy and was compared with teratological sup mutants of A. thaliana.

Key Results

In Carica development of bisexual flowers was similar to wild (unisexual) forms up to locule initiation. Feminization ranges from fusion of stamen tissue to the gynoecium to complete carpeloidy of antepetalous stamens. In A. thaliana, partial stamen feminization occurs exclusively at the flower apex, with normal stamens forming at the periphery. Such transformations take place relatively late in development, indicating strong developmental plasticity of most stamen tissues. These results are compared with evo-devo theories on flower bisexuality, as derived from unisexual ancestors. The Arabidopsis data highlight possible early evolutionary events in the acquisition of bisexuality by a patchy transformation of stamen parts into female parts linked to a flower axis-position effect. The Carica results highlight tissue-fusion mechanisms in angiosperms leading to carpeloidy once bisexual flowers have evolved.

Conclusions

We show two different developmental routes leading to stamen to carpel conversions by late re-specification. The process may be a fundamental aspect of flower development that is hidden in most instances by developmental homeostasis.     

Fractionation and purification of the enzymes stored in the latex of Carica papaya

The latex of the tropical species Carica papaya is well known for being a rich source of the four cysteine endopeptidases papain, chymopapain, glycyl endopeptidase and caricain. Altogether, these enzymes are present in the laticifers at a concentration higher than 1 mM. The proteinases are synthesized as inactive precursors that convert into mature enzymes within 2 min after wounding the plant when the latex is abruptly expelled. Papaya latex also contains other enzymes as minor constituents. Several of these enzymes namely a class-II and a class-III chitinase, an inhibitor of serine proteinases and a glutaminyl cyclotransferase have already been purified up to apparent homogeneity and characterized. The presence of a beta-1,3-glucanase and of a cystatin is also suspected but they have not yet been isolated. Purification of these papaya enzymes calls on the use of ion-exchange supports (such as SP-Sepharose Fast Flow) and hydrophobic supports [such as Fractogel TSK Butyl 650(M), Fractogel EMD Propyl 650(S) or Thiophilic gels]. The use of covalent or affinity gels is recommended to provide preparations of cysteine endopeptidases with a high free thiol content (ideally 1 mol of essential free thiol function per mol of enzyme). The selective grafting of activated methoxypoly(ethylene glycol) chains (with M(r) of 5000) on the free thiol functions of the proteinases provides an interesting alternative to the use of covalent and affinity chromatographies especially in the case of enzymes such as chymopapain that contains, in its native state, two thiol functions.     

低温弱光对以色列番茄幼苗生长及生理指标的影响

用以色列引进品种F-044和安徽省地区主栽品种皖红3号番茄为材料,研究在不同低温(10℃/5℃)弱光(60μm ol.m-2.s-1)处理下及恢复过程中,番茄幼苗生长及生理指标的变化。结果表明:各处理指标变化趋势相同;10℃低温弱光处理后,番茄幼苗生长势、叶片叶绿素含量及超氧物歧化酶(SOD)、过氧化氢酶(CAT)活性下降,而过氧化物酶(POD)活性、丙二酶(MDA)含量,根冠比上升。各指标在恢复期内均能恢复到对照水平;5℃低温弱光胁迫后,F-044仅地上部分干物质积累受胁迫影响,根冠比上升了14.97%,而皖红3号因地下干物质积累减少显著,根冠比则下降了27.74%;各处理下F-044的各项指标变化、恢复情况均显著好于皖红3号,低温弱光耐性强于皖红3号。     

Female Control of Offspring Sex Ratios Based on Male Attractiveness in the Guppy

The sex allocation hypothesis predicts that females manipulate the offspring sex ratios according to mate attractiveness. Although there is increasing evidence to support this prediction, it is possible that paternal effects may often obscure the relationship between female control of offspring sex ratios and male attractiveness. In the present study, we examined whether females played a primary role in the manipulation their offspring sex ratios based on male attractiveness, in the guppy Poecilia reticulata, a live‐bearing fish. We excluded the paternal effects by controlling the relative sexual attractiveness of the male by presenting them to the females along with a more attractive or less attractive stimulus male. The test male was perceived to be relatively more attractive by females when it was presented along with a less attractive stimulus male, or vice versa. Subsequently, test male was mated in two different roles (relatively more and less attractive) with two females. If females were responsible for offspring sex ratio manipulation, the sex ratio of the brood would be altered on the basis of the relative attractiveness of the test male. On the other hand, if males play a primary role in offspring sex ratio manipulation, the sex ratios would not differ with the relative attractiveness of the test male. We found that females gave birth to more male‐biased broods when they mated with test males in the attractive role than when they mated with males in the less attractive role. This finding suggests that females are responsible for the manipulation of offspring sex ratios based on the attractiveness of their mates.     

雌性和雄性虎纹捕鸟蛛粗毒蛋白质含量比较分析

自然界虎纹捕鸟蛛雌蛛数量远多于雄蛛数量,为了探究雌、雄蛛粗毒的差异,用不同方法比较了单个虎纹捕鸟蛛雌、雄蛛粗毒的特征.雌蛛单次螫毒量为(26.5±2.47)μL,冻干后粗毒质量为(5.01±0.78)mg,明显高于雄蛛单次螫毒量(10.83±1.35)μL,冻干后粗毒质量(2.05±0.17)mg;用Lowry法和Bradford法测定雌蛛和雄蛛粗毒的蛋白质含量,两种方法均表明雄蛛粗毒中蛋白含量高于雌蛛.用反相高效液相色谱分离雌蛛和雄蛛粗毒蛋白,并215 nm检测色谱图,发现大部分洗脱峰重叠,而雄蛛色谱图中多两个主峰.Tricine SDS-PAGE电泳分析表明雌蛛粗毒相对分子质量小于10 kD的蛋白质含量较高;而Tris SDS-PAGE电泳分析表明雌蛛粗毒相对分子质量大于10 kD的蛋白质含量较低,基于雌蛛和雄蛛粗毒蛋白含量的差异,有必要对虎纹捕鸟蛛雌、雄蛛粗毒进行独立研究.